How to change proxy information on ubuntu server

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New motherboard has come and I ask my friend to install Ubuntu Hardy . Everything is fine except proxy section when I try to apt-get update.

# apt-get update

Err hardy-security Release.gpg
Could not resolve ‘;3128’
Err hardy-security/main Translation-en_US
Could not resolve ‘;3128’
Err hardy-security/restricted Translation-en_US
Could not resolve ‘;3128’
Err hardy-security/universe Translation-en_US
Could not resolve ‘;3128’

As you see proxy information is incorrect, there is a ; sign not :

To fix it just declare new proxy info and export it.

# http_proxy=
# export http_proxy

Testing again :

# apt-get update

Get:1 hardy-security Release.gpg [189B]
Get:2 hardy Release.gpg [189B]
Get:3 hardy-updates Release.gpg [189B]
Get:4 hardy-security Release [58.5kB]
Get:5 hardy Release [65.9kB]
Get:6 hardy-security/main Packages [203kB]
Get:7 hardy-updates Release [58.5kB]
Get:8 hardy/main Packages [1178kB]
Get:9 hardy-security/restricted Packages [8437B]
Get:10 hardy-security/main Sources [32.3kB]
Get:11 hardy-security/restricted Sources [901B]
Get:12 hardy-security/universe Packages [99.9kB]
Get:13 hardy-security/universe Sources [14.5kB]
Get:14 hardy-security/multiverse Packages [12.2kB]
Get:15 hardy-security/multiverse Sources [1104B]
Get:16 hardy/restricted Packages [6986B]
Get:17 hardy/main Sources [338kB]
Get:18 hardy/restricted Sources [1488B]
Get:19 hardy/universe Packages [4293kB]
Get:20 hardy/universe Sources [1323kB]
Get:21 hardy/multiverse Packages [179kB]
Get:22 hardy/multiverse Sources [60.9kB]
Get:23 hardy-updates/main Packages [474kB]
Get:24 hardy-updates/restricted Packages [8409B]
Get:25 hardy-updates/main Sources [118kB]
Get:26 hardy-updates/restricted Sources [941B]
Get:27 hardy-updates/universe Packages [215kB]
Get:28 hardy-updates/universe Sources [44.3kB]
Get:29 hardy-updates/multiverse Packages [29.3kB]
Get:30 hardy-updates/multiverse Sources [5401B]
Fetched 8832kB in 7min27s (19.7kB/s)
Reading package lists… Done